Abrasive –
Substance used to cut and polish rocks.
Often (incorrectly) called ‘grit.’

Adit – A
mine entryway; usually horizontal.

Agate – Agate is a
type of microcrystalline quartz called chalcedony or cryptocrystalline quartz. This means that individual crystals are to
small to see with your eye. Agate is the
most common variety of chalcedony. Agate
is, in fact, identical with quartz in composition and physical properties. There are many, many varieties of agate (e.g., banded, fortification, moss,
picture, plume, etc.), many of which have been used as gems for centuries. Agate usually forms in cavities in volcanic
rocks.

Agate Probe – A metal rod with a handle
used to detect underground agates (as well as jasper and chert).

Amber – A gem made from
hardened resin of ancient trees. After the resin (sap) was buried in the
ground, it turned into a mineral. Valuable as a jewelry/decoration.

Amethyst – A pale purple to violet variety of crystalline
quartz. The color is due to iron compounds.

Cabochon – A rock that has
been cut in such a manner that its top has a smooth domed surface with no
facets. Oftentimes oval or round in
shape.

Calcareous – Composed of calcite or
calcium carbonate.

Calcite – The main
mineral in limestone and chalk. Its chemical name is calcium carbonate.

Canyon – A deep, narrow
valley often formed when a river cuts through rock.

Carat – The standard
measure of weight for precious gems and minerals. One carat is equivalent to 0.006 ounces (0.2
grams).

Carboniferous – Geological time period
that stretches from around 365 – 290 million years ago.

Cast – A fossil formed by the infilling
of a mold. For example, ‘wood casts’ may
form where trees or parts are buried, then disintegrate, and agate fills the
void.

Cat’s-eye effect – See chatoyancy.

Cave – A naturally formed opening in
the ground that extends beyond the zone of light and is large enough for a
person to enter.

Cavern – A large chamber within a cave.

Chatoyancy – An optical effect popularly known as ‘cat’s-eye
effect’ in which certain gemstones, when polished, will reflect bright light as
a single, thin ray (like a cat’s eye pupil).
Chatoyancy is caused by fibrous inclusion that run parallel to one
another. Rounding the stone (a polished cabochon
or sphere) concentrates the light and increases the effect. Polished tiger’s eye quartz, for example, can
exhibit chatoyancy.

Chemical Sedimentary Rock – Rock that is formed by mineral precipitation.

Chitin – The horny substance that forms
the shell of arthropods.

Cinder Cone – The naturally expelled
debris, usually in a conical pile, surrounding the vent of a volcano.

Cirque – A steep-sided,
bowl-shaped hollow in a mountain, carved out by a glacier.

Concentrates – Material that has been
processed (e.g., washed, screened) and therefore reduced typically by removing
large rocks and organic material.

Conchoidal – Term used to describe a
concave (curved or shell-like) fracture in a glassy mineral. For example, obsidian will make a conchoidal
fracture.

Concretion – A distinct, hard, compact mass or aggregate of mineral
matter that normally is rounded but may be very odd shaped. They usually are formed by chemical
precipitation.

Conflict Minerals – Minerals (especially diamonds and other
gemstones) that are mined in war zones to finance terrorist or revolutionary
groups.

Conglomerate – Sedimentary rock made up of
pieces of rocks that have been worn into rounded shapes (essentially the same
size) that have been naturally cemented together. Also known as puddingstone.

Conodonts – Teeth of very
early fish-like creatures that lived about 515 million years to 210 million
years ago.

Contact Metamorphic Rock – Rock that forms as the heat from magma or a lava flow alters an existing
rock.

Coprolite – Fossilized dung.

Coral – This gem comes
from the skeletons of tiny sea animals that live in colonies. A coral
polyp takes up calcium carbonate minerals from the sea and builds itself a hard
limestone home. The most valuable coral is red.

Core – The center of the earth, made of
heavy metals. It is about 850 miles across.

Country Rock – The rock that surrounds
a mineral deposit or igneous intrusion.

Crater – The natural depression marking
the vent of a volcano or impact site of a meteorite.

Craton – Ancient part of a continent
unaltered for at least one billion years.

Cretaceous – Geological time period
that stretches from about 145 – 65 million years ago.

Crinoids – A large class
of echinoderms usually having a somewhat cup-shaped body with five or more
feathery arms.

Crust – The thin outer
rocky layer of the earth that lies over the mantle. The crust is between four and forty-four
miles thick. There are two main types of
crust: continental and oceanic. Continental
crust is thicker than oceanic crust.

Cryptocrystalline – Describing a rock
surface or solid rock that is comprised of extremely minute or microscopic
crystals.

Crystal – The special
shape (geometric form) in which many minerals form. A crystal has fixed properties and the sides
usually are flat and regular. For
example, a quartz crystal has six sides.

Crystal Form – The way in which the
different faces of the crystals are arranged.

Crystal Habit – The typical shape in
which a crystal or cluster of crystals grows.

Crystal System – One of the different
groups into which crystals may be placed according to how they are symmetrical.

Dana Number – Number assigned to each mineral according to the
classification system devised by James Dwight Dana.

Dendrites – Fern-like
growths of crystals found lining the cracks and joints in rocks.

Deposit – To lay down a
material such as mud, sand, or gravel in a new location.

Desert – An arid region
that typically receives less than ten inches of rain a year.

Devonian – Geological time period that
stretches from about 415 – 360 million years ago.

Diatom – Fossilized microscopic marine
plant.

Dichroic – Showing different colors when viewed
from different directions. Certain forms
of tourmaline are dichroic.

Dike (sometimes Dyke) – A sheet-like igneous
intrusion that is near vertical or cuts across existing rock.

Dinosaurs – The group of
now extinct prehistoric reptiles that lived between 230 and 65 million years
ago. Their closest living relatives include crocodiles and birds.
Yep, birds.

Dip – The downward angle of inclination
of bedrock from the horizontal.

Doublet – A composite
stone made of two pieces cemented or glued together - e.g., opal doublets.

Dredge – Mining equipment used to find
gold, sapphires, or garnets. Typically,
dredges are used in streams to suction up material from the streambed to
process through a riffle or other device to screen out heavy material (e.g.,
gold).

Drusy – A crust of uniformly tiny
crystals filling a cavity or coating a rock.

Dumpsite – At a mine site, where the
non-economic rocks are deposited.
Rockhounders often will search dumpsites as these piles will contain
material that took enormous effort to bring to the surface and may contain
interesting specimens.

Electrum – A natural mixture of gold and silver.

Element – Material that
cannot be broken down into more simple substances by chemical means. The simplest, most basic substances – such as
gold – each with its own unique atom.

Enhydro – A crystal that contains a
fluid-filled cavity.

Eocene – Relating to, or
being an epoch of the Tertiary Period between the Paleocene and the Oligocene
or the corresponding system of rocks. About 55 to 35 million years before the
present.

Epoch – Division of geological time,
part of a period.

Era – Largest division of geological
time lasting hundreds of millions of years.

Erosion – The wearing
away (eroding) and removal of exposed material by water, wind, and ice.

Erratic – A large rock
that has been carried by a glacier and dropped from its place of origin. We have a couple of large erratics in our
yard (one is about half the size of a car).

Erosion – The wearing away of the
material on the Earth’s surface.

Eruption – A discharge of lava,
pyroclastic material, or gas from a volcanic cone or vent.

Evaporite – A natural salt
or mineral formed by the process of evaporation (gypsum, halite).

Extrusive Igneous Rock – Igneous
rock that forms at the earth's surface.
The type of rock that forms when volcanic lava cools and solidifies.

Facet – Flat surface on
a cut gemstone.

Fairy Cross – Twin crystal of
staurolite.

Fault – A long fracture in rock along
which rock masses move.

Feldspar – Feldspars are the most common, rock-forming minerals
and constitute 60 percent of the earth’s crust.
They include gem varieties such as labradorite and they weather over
time to produce clays.

Feldspathic – Rock containing feldspar.

Felsic – Rock rich in feldspar and silica,
typically light in color.

Fire Agate – Fire agate is a
form of chalcedony that contains inclusion of iron oxides that result in a play
of colors much like that of precious opal.

Fissure Volcano – Volcano that erupts through a long crack.

Float – Pieces of rock that have moved from their original source.

Flood Basalt – Plateau formed from huge eruption of basalt from
fissure.

Flowstone – The general term for the sheet-like mineral deposit on a
cave wall or floor.

Fluorescence – The emission of brightly colored light by a substance
when exposed to ultraviolet light rays.

Foliation – Flat layers of minerals in metamorphic rock formed as
minerals recrystallize under pressure.

Fool’s Gold – Pyrite. Named so
to emphasize that pyrite is not gold.

Formation – A related deposit of rocks formed during the same time
period and under generally the same circumstances.

Fortification – A form of agate with angled concentric banding.

Fossil – The remains, traces,
or impressions of organisms (plants and animals) that lived millions of years
ago and usually are preserved in rocks. Some
of the oldest fossils are trilobites which can be up to 500 million years old
which is much older than dinosaurs.

Fossil Fuels – The fuels coal,
oil, and natural gas all of which are formed from the remains of once-living
organisms.

Fracture – The way in which a rock or
mineral breaks when it does not break along cleavage planes.

Fulgurite – Sand fused by lightning.

Fumarole – A hole or vent through which
a volcanic gases escape.

Gangue – Waste
rock in a mineral deposit that is being worked.

Gastroliths
– Stones, swallowed by dinosaurs and other animals, used to help grind up food.

Geode – A rock
containing a crystal-lined cavity in which the crystals grow toward the
center. Typically, a portion of the
geode is hollow, but lined with quartz.
Geodes occur in lava or limestone.

Geologic Time Chart – Record of
divisions of the Earth’s history.

Geological Column – Diagram depicting
the successive layers of strata that have formed over geologic time, with the
oldest at the bottom and the youngest at the top. Grand Canyon, Zion, and Bryce Canyon National
Parks use geological columns to explain the formations and the relationships
between the Parks.

Geologist – Someone who studies
the earth. Often times, geologists study rocks and fossils to learn more
about the earth’s history.

Glacier – A large mass of
ice that forms on land and flows slowly downhill under its own weight.

Gold Dore – A bar of gold that usually
is about ninety percent pure but also includes other metals. These bars are subsequently smelted and
treated to remove the unwanted metals to achieve 0.999 fine gold.

Grain – A particle of a
mineral. Rocks can be described as fine grained or coarse grained
depending on the size of the particle.

Graphite – A mineral made
entirely of the element of carbon. Graphite is very soft and black.

Grubstake – Supplies furnished to a
prospector in return for a share in discoveries. A good reason to take an extra candy bar when
rockhounding.

Habit – The general
shape or appearance of a mineral.

Hackly Fracture – Jagged breakage
surface of a metal.

Hardness – Degree of resistance of a
rock or mineral surface to being scratched.
The relative hardness Mohs scale uses a 1-10 scale.

Horn – A steep-sided mountain peak, formed
by erosion by several glaciers.

Ice Age – For rockhounds, the Ice Age usually
refers to the most recent ice age - a portion of the Pleistocene epoch that
began about 1.8 million years ago and ended about 11,000 years ago. During this time, the Earth went through a
series of cold climates in which much of North America was covered by glaciers.

Ichnofossils – Ichnofossils (or trace fossils) are typically sedimentary structures
consisting of a fossilized track, trail, burrow, or tube resulting from the
life activities and behavior of an animal, such as a mark made by an
invertebrate creeping, feeding, hiding, or resting on or in soft sediment. Some non-sedimentary examples include tooth
marks (resulting from predation), skin impressions, and coprolites (fossil
dung).

Igneous Rock – A type of rock
that forms as lava or magma cools and hardens.
Extrusive igneous rock forms on the earth's surface from lava. Intrusive igneous rock forms underground, in
the earth's crust, from magma.

Impact Crater – Crater formed by the
impact of a meteorite.

Inclusion – The presence of
a foreign body within the a crystal (example – rutile in quartz crystal).

Japan Law Twin – Twin quartz crystals joined in the same plane at an
angle of about 84 degrees.

Jet – A form of coal that can be polished
to look like black glass.

Jurassic – Geological time period that stretches
from about 200 – 145 million years ago.

K-T
Extinction (K-T Boundary Event) – Approximately 65 million years ago, at the end
of the Cretaceous and just before the beginning of the Tertiary, the fossil
record suddenly changes. At this time,
approximately three-quarters of all life forms go extinct. The “K” refers to Kreide, meaning chalk in
German and references the chalky sediment layer from that time. The “T” refers to Tertiary.

Karat –
Parts per 24 of pure gold in an alloy.

Karst
Topography – Geologic formation shaped by the dissolution of a layer(s) of
soluble bedrock. The landscape is
characterized by the presence of sinkholes, caves, springs, and underground streams.

Kimberlite
– Igneous rocks rich in volatiles, normally forming pipes.

Knapping – The process of chipping away at a
stone (such as flint, agate, chert, obsidian) to produce projective points,
knives, and other objects.

Laccolith – A mass of intrusive igneous rock with a dome-shaped top and
generally flat base.

Lava – The hot melted rock that flows out
of an erupting volcano. Inside the
volcano, the melted rock is called magma.

Lava Tube – A hollow formation created
not by erosion but rather when molten lava solidifies on the exterior but the
insulation allows the interior to continue to flow and empty creating a hollow
tube.

Leaverite – Rockerhounder
slang for a rock that isn't worth carrying back home; just leave 'er right
there.

Lithophysae – Scientific name for a thunderegg
(Latin for ‘rock bubbles’).

Lithosphere– That portion of the Earth comprising the crust and upper-most portion of the solid mantle.

Luster – The way a
mineral shines caused by reflected light.
Various terms such as metallic or
resinous, bright or dull may be used to describe the luster of a mineral.

Mafic – Rocks rich in magnesium and ferric (iron) compounds.

Magma – The hot, molten
rock deep in the earth's crust that becomes lava on the surface.

Magma Chamber – Underground reservoir
of magma beneath a volcano.

Mantle – Layer of the
earth between the outer core and the crust.
It is approximately 1,800 miles thick.
The mantle is made of solid rock that is very hot and slightly viscous,
allowing it to flow and circulate over long periods of time.

Massive – Having no definite crystal
form or structure.

Matrix – The mass of
rock in which larger crystals or fossils are embedded. Also known as
groundmass.

Metamorphic Rock – A type of rock
that has been changed by intense heat and/or pressure causing physical and
chemical changes as well as the partial melting and recrystallizing of its
minerals.

Metamorphism – Process by
which rocks and minerals are transformed by heat and pressure to create a new
rock.

Meteor – A rock from
space that burns up as it enters the earth's atmosphere.

Meteorite – A piece of rock
from space that hits the earth's surface without completely burning up.

Microcrystalline – A mineral
structure in which the crystals are too small to be seen with the naked eye. You need a microscope to see the crystals.

Micrometeorite – A microscopic
meteorite.

Micromount – Small mounted rock or
mineral.

Mineral – A naturally occurring, inorganic element or compound having an
orderly internal structure and characteristic chemical composition, crystal
structure, and physical properties. Minerals are the building blocks
of rocks. Accordingly, all rocks
are made from minerals.

Mineral Vein – Cracks in rocks
that become filled with hot, mineral-rich liquids.

Mineralogist – A scientist who specializes in the study of minerals.

Mineralogy – The study of rock forming minerals.

Mohs' Scale – A scale devised
by the Austrian mineralogist Friedrich Mohs that measures the relative hardness
of minerals.

Mold – The fossilized imprint of the
body of an organism.

Moqui Marble – A dark brown concretion
that weathers out of the Navajo Sandstone Formation in southern Utah. The concretions form when groundwater
containing iron flowed through the formation and precipitated out as iron
oxides.

Moraine – An accumulation of debris
deposited by the outermost edge of a glacier.
Our yard. Seriously. A two hundred foot deep gravel deposit from
the end of the last ice age.

Mother Lode – The principal vein or
lode; the richest and largest source of a desired mineral.

Mudstone – Sedimentary rock composed of
fine-grained particles.

Nacre – Tiny platelets
of calcium carbonate that create the soft sheen on pearls and inside some sea
shells as they reflect light.

Native Element – Element that occurs
naturally uncombined with any other element.

Nodule – A rounded lump
of mineral found in sedimentary rock.

Ocean Spreading – Process in which oceans widen as new rock is brought
up at the mid-ocean ridges.

Oolith – Small, rounded
grains (usually calcareous) that make up some sedimentary rocks.

Oolitic – Made mostly of ooliths.

Opaque – Describing a rock or mineral
through which light does not pass.

Outcrop – A geologist’s term for the area in which rocks are
exposed at the earth’s surface.

Oxidation Zone – Upper layer of mineral deposit
where minerals are altered by oxygen and acids in water. This process also is why dad has to
power-wash the large glacial erratics in our yard so that they look nice.

Paleoecology – The study of the ecology of fossil animals and plants.

Paleontology – A science
dealing with the life of past geological periods as known from fossil
remains.

Pegmatite – Very
coarse-grained igneous rock similar to granite in
chemistry but characterized by very large mineral crystals, usually found in veins and pockets around large
plutons and rich in rare minerals. Some pegmatites have feldspar, quartz, or other
mineral crystals of extraordinary size.

Penguin Motto – No one swims
alone. Smart rockhounders follow the Penguin Motto and go rockhounding
with a buddy. That way, in the event of
injury or a problem, there is help.

Period – A division of
geological time lasting tens of millions of years.

Permian – Geological time period that
stretches from about 300 – 250 million years ago.

Petrology – A branch of geology that deals with the origin,
occurrence, structure, and history of rocks.

Phaneritic – Grains visible with the naked eye.

Phantom – Earlier growth enclosed within a
crystal.

Phenocryst – A relatively large crystal in
igneous rock.

Piezoelectricity – Electricity produced in a
crystal by pressure.

Pillow Basalt – Lava formed on the seabed consisting
of pillow-shaped formations created when molten material contacted water. Crystals often occur in the cavities of
pillow lava.

Placer – Natural deposit of valuable
minerals such as gold washed into loose sediments such as river gravels. Gold found in its natural state without any
host rock. Placer gold (dust or nuggets)
typically is found in streams (current or historic) where it has washed away from
its source.

Plate – A large
fragment of the earth's crust. Also known as a tectonic plate.

Plug – The solidified core of an
extinct volcano.

Pluton – Any large mass of igneous rock
that formed beneath the Earth’s surface by solidification of magma.

Polymorphs – Different minerals created
by different crystal structures of the same chemical compound.

Porphyritic – Igneous rock containing
lots of phenocrysts.

Properties – The characteristics of rocks or minerals by which they
may be identified.

Pry Bar – A steel tool used to move
heavy rock or expand a crack. A ‘crow
bar’ is a type of pry bar.

Psammology – The branch of geology
relating to the study of sand.

Pseudofossil – A natural object,
structure, or mineral that resembles a fossil, but actually is not a fossil. Common pseudofossils include manganese dendrites
that form tree-like or fern-like patterns.
Other common pseudofossils include flint and chert nodules, pyrite ‘sun
dollars,’ and some concretions.

Pseudomorph – A crystal with the
outward form of a different mineral species.
The term also is used to describe other substitutions such as petrified
wood where quartz becomes a pseudomorph of wood.

Pumice – A bubbly lava that has
solidified in a light, frothy state (sometimes light enough to float on water).

Rock Cycle – The continuous
cycle through which old rocks are transformed into new ones. For example,
an igneous rock may erode and the material becomes a sedimentary rock that may
then become a metamorphic rock that may then erode and so on.

Rock Saw – Generally speaking,
there are two types of rock saws: slab
saws and trim saws. The primary
difference is size. Generally, a trim
saw has a blade that is four to ten inches in diameter whereas a slab saw has a
blade that is ten inches or more in diameter.
Rock saws use circular disk blades with diamond rims.

Scepter
– For mineral collectors, a scepter is a large crystal capping a slender
crystal stem. Scepters result from an
interruption of crystal growth and are a rare type of crystal formation.

Schiller Effect – The brilliant play of bright colors in a crystal,
often due to minute, rod-like inclusions.

Scree – A mass of loose
rubble and gravel on a mountain slope caused by weathering.

Secondary Mineral – A mineral that
replaces another mineral as the result of a weathering or alteration process.

Sediment – Solid grains that have
settled out of water.

Sedimentary Rock – A type of
rock that originates on the Earth’s surface and forms when sediment is compressed
and cemented. It consists of layers of
rock fragments or other substances (e.g.,
sea shells) that have been deposited on top of each other.

Sill – Sheet-like igneous intrusion
either near horizontal or following existing rock.

Smelting – The process by
which a metal is removed from an ore.

Specific Gravity – The ratio of the
mass of the mineral to the mass of an equal volume of water. Specific gravity is numerically equivalent to
density (mass divided by volume) in grams per cubic centimeter.

Stalactite – An
icicle-shaped mineral deposit hanging from the roof of a cavern or cave.

Stalagmite – An upside down
icicle-shaped mineral deposit that rises from the floor of a cavern or cave.

Stope – The series of ‘steps’ above or
below a mine level where ore has been extracted.

Strata – A sequence of
rock formations that can informs us of geological processes over time.

Stratification – Bedding in sedimentary
rock.

Streak – The color that
a powdered mineral makes when rubbed across an unglazed tile. The streak is a useful clue to identify
a mineral.

Strewn Field – The geographic area on
the surface of the Earth where meteorites from a single fall are dispersed.

Striation – A minute parallel groove or
line on a crystal face. Pyrite, for
example, may display an obvious striation.

Stromatolite – A rocklike mound
produced by microorganisms growing in shallow water. Fossilized stromatolites are among the oldest
signs of life on Earth.

Subduction Zone – Boundary between two
tectonic plates where one plate descends into the mantle beneath the other.

Talus – A
sloping heap of naturally fallen debris at the base of a mountain or cliff.

Tectonic – The geological
processes within the earth that affect the earth's crust.

Tectonic Plate – One of the
approximately two-dozen giant slabs into which the Earth’s rigid surface is
split.

Tektite – Glassy rock formed by a meteorite impact.

Thunderegg – A volcanic nodule that typically features
a rhyolitic outer shell and a central core of agate, opal, and/or crystals. The scientific name for a thunderegg is
lithophysae (Latin for ‘rock bubbles’).

Topographic Map – A map of an area that depicts mountains and valleys by
using ‘topographic contour lines.’ It
also usually contains information on roads, rivers, towns, and other features
you may come across in a given area.

Topography – The general shape of the surface of the earth,
particularly used to define to the shape of the hills and valleys.

Translucent – Description of
a material that light is able to pass through, but that is not clear enough to
look through.

Transparent – Clear enough to
look through.

Trichroic – Showing three different colors when
viewed from different directions. Natural
tanzanite is trichroic.

Trilobites – A group of prehistoric
arthropods named after the three lengthways lobes of their bodies. Trilobites lived in the sea and survived for
over 250 million years.

TV Stone – See Ulexite.

Twin Law – Law stating the way in which
the parts of a twin crystal are related.

Twinned Crystals – Two or more
crystals of the same mineral that intersect each other along a common, or
shared, plane.

Ulexite – A borate mineral composed of
long, thin crystals that often occur as a blocky mass of fibrous veins. When cut and polished (perpendicular to the
crystal fibers), and placed on top of a page of text, the text will appear at
the top of the specimen. The individual
crystals that make up the specimen will transmit light from the bottom surface of
the specimen to the top surface, which resulted in the popular term ‘TV Stone.’

Ultramafic
Rock – Igneous rock with a silica content of less than 45%. Also known as ultrabasic rock.

Ultraviolet
Light – A type of light that is long or short wave that is used to identify
rocks that fluoresce (or glow) in a variety of colors.

Vein – A thin, sheet-like fracture in a rock that is filled
with secondary minerals such as quartz or calcite.

Vertebrates – Animals with a
backbone or spinal column. Dinosaurs were vertebrates. Vertebrate fossils
are regulated differently than invertebrate fossils.

Vesicle – Small cavity in
extrusive igneous rocks that is left by a gas bubble as the rock hardens.

Vitreous Luster – A shine resembling
that of glass.

Volcano – A vent or
fissure in the earth's crust through which molten rock and hot gasses escape.

Volcanic Bomb – Blob of lava
thrown out of a volcano. It solidifies
before hitting the ground.

Vug – A cavity in rock, often lined with
crystals.

Waxy
– One of
the technical terms used to refer to the luster of a gemstone. Turquoise is an example of a gem with a waxy
luster.

Weathering – The breaking
d
down of rocks and minerals by the action of various
natural processes. Mechanical
weathering, for example, occurs when heat, water, ice, and pressure act upon
rock surfaces. Chemical weather occurs
when chemicals in the atmosphere or environment interact with the chemicals in
rocks and minerals (carbon dioxide dissolved in rainwater produces a weak acid
that can dissolve rock).

Xenolith –
Country rock enclosed in magma.

Yellowcake – The solid form of mixed uranium oxide, which is produced
from uranium ore in the uranium recovery (milling) process. The material is a mixture of uranium oxides,
which can vary in proportion and color from yellow to orange to dark green
(blackish) depending on the temperature at which the material is dried (which
affects the level of hydration and impurities), with higher drying temperatures
producing a darker and less soluble material.
The yellowcake produced by most modern mills is actually brown or black,
rather than yellow, but the name comes from the color and texture of the
concentrates produced by early milling operations.

Zeolite – Zeolites are
minerals that have a micro-porous structure.
Natural zeolites form where volcanic rocks and ash layers react with
alkaline groundwater. Zeolites also
crystallized in post-depositional environments over periods ranging from
thousands to millions of years in shallow marine basins. Naturally occurring zeolites are rarely pure
and are contaminated to varying degrees by other minerals, metals, quartz or
other zeolites.